The invention relates to a squirrel cage rotor for an asynchronous machine, said rotor comprising a laminated rotor core having shorting rings which are cast onto the end faces of the laminated rotor core. The invention is concerned in particular with the cooling system of such a squirrel cage rotor.
In addition, the invention relates to a method for producing such a squirrel cage rotor in which a corresponding cooling system is provided.
In order to increase the efficiency of an electrical machine, various cooling techniques are used in which the heat produced in the stator and rotor is dissipated to the surroundings. The temperature rise in the rotor is generally greater than in the stator. It is more difficult, however, to remove the heat from a rotating component such as the rotor.
A squirrel cage rotor for an asynchronous machine is known from DE 43 08 683 A1 and comprises shorting bars which are arranged in slots of a laminated rotor core and, at the two end faces of the laminated rotor core, are connected mechanically and in an electrically conducting manner to shorting rings produced in the aluminum die-cast process.
A routine method for dissipating heat from a rotor of this type is to design the shorting ring to have blades in order to enable heat dissipation from the motor interior. The effectiveness of such a cooling method depends on the speed of the motor. The blades on the shorting ring become less effective at dissipating heat as the number of poles in a machine increases. The effectiveness of such a cooling method also reduces with the axial length of the laminated rotor core because it then becomes increasingly difficult to enable sufficient heat removal along the entire rotor core length.